Automatic thread-tension-releasing means for sewing machines



Jan. 30, 1923.

A. c. CROFFORD. ON RELEASING MEANS FOR SEWING MA CHINES.

AUTOMATIC THREAD TENS! HLED AUG-l9,192l.

7 BY 1T0 I A TTORNEYT ing machines.

Jan. 30, 19.23.

naura' r TES ADA o. onorronn, or CODY, NEBRASKA PATENT" OFFICE.)

AUTOMATIC TI-IREAD-TENSION-RELEASING I /IEANS FOB, SEW'ING'MACHIINES. v

Application filed August 19,1921. Serial No,493,618.

T066 wlzmnit may concern:

Be it known that 1, Ann C. Cnorronn, a citizen otthe United vStates, residing at Cody, inthecounty of Cherry and State of Nebraska, have invented certain new and useful Improvements in Automatic Thread- 'lension-Releasing Means for Sewing Machines, oi? which the :l'ollowing a specificaby the needle bar operating shaft, a swing:-

constructions ing dog' which. will not be effective during the normal operation of the machine but which, when the machine is turned backwardly,' will, in effect, become rigid with the cam and engage a special lever or spring which is so related to the upper thread tension ,as to release said tension when this action occurs.

My invention is not limited to the specific hereinafter described and shown in the drawings as the principle of the invention may be applied in other ways, with or without the use of additional mechanical parts. I

In the accompanying drawings:

Figure l is a side elevation, broken away, showing the invention applied to a sewing machine and v i i Fig. 2 is a section on line 22, Fig. 1.

The hollow head which contains the needle bar and pressor foot is shown at 1. v

The needle bar operating shaft, 2 terminates in the hollow head 1 and carries the cam plate 3. i

The upper thread tension appears at 4. This is provided with a stem 5 which passes freely through the wall of the head 1 and carries a coil spring 6 which tends to hold the stem in normal position and to render the tension operative.

Secured to the head 1 and arrangedvvertically therein is a releasing member 7 which is normarly spaced or separated from the- ,arc of a circle shaft 2.

end of the stem but may be pressed against said stem for the purpose of compressing the spring 6 and releasing the thread tension 4. The releasing member 7 when made in the form shown is a fiat spring whoselower end is fixed to the head 1 as at 8 and whose lower portion "is free and rises within said head; being provided with a curved portion 9 which lies in the Pivoted at 10 to the cam plate 3 is a dog 11 which may fold into the recess or cavity 12 in the cam plate and which when thrown outwardly, is arranged so that its tail will engage a shoulder 13 on the cam plate so that the dog will be rigid with the latter, if the shaft 2 is turned backwardly and the dog engages the releasing member 7. 1

During normal rotation of the shaft 2 and cam plate 3, the dog 11 is kicked back into folded position when it makes contact with the releasing member 4.

and cam plated rotate in reverse direction thereby throwing out the dog 11 until its tail engages the shoulder 13 whereupon the dog is rigid with the cam plate and as it engages the curved part 9 of the releasing member 7, pressing hack the releaslng member and causing it to engage the stem or post thus releasingthe tension 4. The tension remains in released condition by reason of the length of the curve 9, until the dog clears the member 7 a I am aware that the releasing member 7 i bar operating shaft, a releasing device adapted to cooperate with the threadten sion and a dog carried by the shaft, said dog being kicked ,baekwardly by the releasing device during normal operation of the said shaft and rendered operative for the purpose of engaging the releasing device when said shaft is turned hackwardly.

2. In a sewing machine the combination struck from the center of the VVhen however, the machine is turned backwardly, the shaft I with a"thread-tension, of a rotary needle operating shaft having a cam a dog pivoted to said earn and adapted to be thrown outwardly, the cam having aehoulder with which the dog is adapted to engage when thrownoutwardly, and a releasing device adapted to cooperate with said thread .ten-

sion and having a curved part with which said dog is adapted to engage, said dog be- ,ing kickedtbackwardly v .1 YlCQJdllllDg normal operation of said bythe releasing deshaft and madearigid with the cam by engaging the shoulder when the shaft is turned backavardly, thereby "pressing back the releasing device. 3 In a sewinginachine, the coinblnatlon with the needle operating shaft, and a cam Fcarried by theaend of said shaft, of a releasahle thread tension, and a dog carried tom of the head, isperpendicular thereto,

and so placed as to be adapted to be pressed hack against the inner end of the tension stein by the dog on said shaft When the machine is turned backward, to thereby release the tension.

In testimony whereof i afiix my signature.

ADA o. oao'rroan. 

